Classical eyeblink conditioning depends on an identified brainstem-cerebellar circuit. The cerebellar cortex has been shown to play a significant role in the learned timing of the classically conditioned eyeblink response. The proposed research will test the hypothesis that differences in conditioned response timing across ontogeny correlate with maturation of the cerebellum and are sensitive to cerebellar damage produced by neonatal alcohol exposure. Two complex timing tasks - ISI discrimination and temporal uncertainty - will be used at different points across development in two experiments. Experiment 1 will attempt to identify the age at which the poorer CR-timing that we've seen in younger rats develops into the more appropriate, well-timed responses seen in adults. Experiment 2 will attempt to identify whether CRtiming is disrupted by neonatal ethanol exposure under conditions that are known to target the cerebellum. This aim will ask whether doses of ethanol lower than those shown to affect gross CR performance are capable of leading to more subtle deficits in CR timing. Experiment 3 will examine cerebellar cell counts in rats from Experiment 2 to confirm cerebellar targeting and examine correlations with behavioral effects. [unreadable] [unreadable] [unreadable]